Pulverized-fuel furnace and method of operating the same



Get 27,1931.

E. HAVEAUX 1,829,445

PULVERIZED FUEL FURNACE AND METHOD OF OPERATING THE SAME Filed March 7, 1928 2 Sheets-Shet l 0C?- 27, 1931. H U 1,829,445

PULVERIZED FUEL FURNACE AND METHOD OF OPERATING THE SAME Filed March '7, 1928 2 Sheets-Sheet 2 Patented Get. 27, 1931 UNITED STATES PATENT OFFICE EMILE HAVEAUX, 0F VALENCIENNES, FRANCE, ASSIGNOR TO SOCIETE DELECTRICITE DE LA REGION DE VALENCIENNES-ANZIN, OF PARIS, FRANCE, A COMPANY OF FRANCE PULVERIZEID-FUEL FURNACE AND METHOD OF OPERATING THE SAME Application filed March 7, 1928, Serial No. 259,778,

The present invention consists of improvements relating to pulverized coal furnaces for all usages and in particular for the furnaces of steam boilers.

The improvements which form the subject of the present invention have for object:

(1) To provide at the lower part of the combustion chamber a heat-intercepting screen formed by a layer or stratum of air from the exterior atmosphere drawn continuously across the lower zone of the furnace, the

said layer or stratum of air being traversed by the ashes which fall from the combustion zone of the furnace and are thus cooled before reaching the ash-pit,

(2) To avoid, by reason of their cooling, any agglomeration of the ashes into compact masses in the ash-pit, and thus to facilitate their removal;

(3) To utilize the air which has served as the screen and of which the temperature at its exit from the combustion chamber may attain 400 to 500 C., by forcing it under pressure as a secondary supply of air into the pipes which feed the powdered coal to the one or more burners of the furnace;

(4) To ensure a better utilization of the coal' (5 To permit the use in the best conditions for efiiciency, of low-grade coal, that is to say coal of low content of volatile matter;

(6) To reduce the dimensions of the combustion chambers.

According to the present invention I create in the lower part of the combustion chamber of apowdered coal furnace a layer or stratum of air which moves in a continuous 'manner and forms a screen through which the present invention.

Figure 1 is a vertical section of the Said and. in France and Great Britain March 26, 1927.

furnace, showing in elevation the means for supplying pulverized fuel to the furnace and for causing heated air to enter the fuel sup ply system, and one bank of water tubes of a boiler heated by the furnace.

Figure 2 is a corresponding horizontal section taken on line 2-2 of Figure 1, showing in plan view the pipe system, collector and blower for drawing ofl' the heated air from the neutral zone of the furnace.

Figure 3 shows a burner in section.

According to the invention, I form in the rear wall a of the furnace combustion chamber A, a certain number of openings 6 which place the said chamber A incommunication' with-the atmosphere, and are intended for the passage of air from the exterior. These apertures b are of suitable dimensions and shape; they may be provided. along the exterior face of the wall a with registers or The blower or fan D by its suction action upon the pipes C 0 0 causes a fall of pressure in the lower part of the chamber A, and this causes the entrance thereinto of atmospheric air through the openings 6. This air moves slowly from the said openings 6 towards the suction nozzles 0, forming at N a continuous layer or stratum which constitutes an effective heat-intercepting screen over the neutral zone portion at the bottom of the chamber A, while leaving said neutral Zone portion in open communication with the upper portion or combustion zone of the chamber.

The cinders falling from the combustion zone of the screen forming layer or stratum which moves continuously at N across the lower zone of the chamber A; they are thereby cooled and can afterwards accumulate in the ash-pit I which is thus itself cooled, without the ashes forming compact solidified near the exit from the burner H, obviating to the greatest possible extent the production of reducing zones inthe stream of pulverized coal.

16 0 into the chamber through the inlets B has masses, which in the case of certain kinds of coal, would entail in present day furnaces considerable difiiculties in connection with their removal. Even with these coals by reason of'thepresent invention, the clnders never form considerable agglomerated masses and aren ever in the pasty state; they are always so friable that their removalcan beeffected inanormal and-practical manner. I I v izer mill G and the quantity of secondary a r During its travel across the'lower zone 0 the chamber A, the air drawn in by the fan D,

is submitted to'heat radiated fromxtheliames" of this furnace, fed by the burner H; it is moreover, incontact' with the cinders which fall from combustion zone of the furnace.

In this'condition, its temperatureprogres sively rises to the pointv that it can easily reach iOO' to 500C, at its entrance' into the nozzles-c.

In accordance with the invention, the air drawn in by the fan or blower is forced by the latter into apipel E which delivers in the form of. an ector nozzle 6 into the pipe F connecting" the coal-.pulverizing nill' G 'with the burner H.

The powdered-coalmill G does not present any special feature. and it works in the usual manner, delivering a certain quantity of primary air which carries with it the powdered coal intended to feed the burner H.

additional airfor combustion being delivered into the combustion zone DQ113101} of the furn ace through inlets B the ear wall a. v

The air drawn across'the lower part of the furnace below the combustion zone portion penetrates into the pipe F under pressure and at a very high temnerature this secondary air mixes intimately with the primary air charged with powdered coal, delivered b the mill G, before reaching the burner H. Whilst this mixing is taking place, the whole of the moisture which the coal may contain is evaporated. H e i Bv reason of this arrangement, the nu]- in the upper portion of verized coal at the moment when it escapes from the burner H and enters into the com- 1 busti on chamber A, is distributed throughout the mixture of primary air and secondary air, and each, particle of coal finds at its side immediately on its entry into the chamber A, I the molecules of ox ygen necessary for its combustion. v i

The combustion of the coal. thus'talres place The additional air introduced as usual solely for effect to improve still more this combustion.

By means of this invention, it is thus poshaving a low content of volatil'ematter; for

injected by the nozzle 6. I In the foregoing description, reference has been made to a type of furnace supplied by a pulverizer mill; but itamust be understood that the improvements which have been describedcan'beapplied in connection with any othermethod of fuel feed, notably ininstallations provided with a central pulveriz' ing plant, the invention comprising "essenti'ally, first, the creation'of a current of air forming a screen at the lower part of the combustion chamber, and secondly, the utilization of the air thus raised to a high temperature by delivering it as a secondary air supply into the pipe fceding'the pulverized "fuel to the burner..

The burner may obviously be of any suitable type whatever: nevertheless, the burner H, represented in Figure 3 of the drawings,

presents the advantage of perfecting the in-='** timate mixture of *air and coal arriving throng pipeF at the veryfmoment when "itis about to enter the chamber A.

i This particular burner H is composed of a plain truncatedconical pipe in in theinterior of;which, near its smaller base, is formed aconvergent truncated cone 71, with no divergent portion. r

It might be feared that under the conditions indicated, the air drawn in by the fan- D might be charged with carbonic gas in a manner incompatible with the purpose for which it is intended. Asa matter of fact it is not so, for the quantity of carbonic gas carried along is quite unimportant and'pra'ctically so small asnot to influence the combustion. j

It has not been previously mentioned that the combustion chamber A 'isprovided with the usual accessories but it is' tofbe understood that such is the case. Further, without departing from "the scope of the invention, the number and the position bothjof the openings 6 and of the suction nozzles '0 can be varied; these nozzles might be connected with either a single fan 1) or with several fans serving the same purpose. Lastly, in place of utilizing a single burner H, several of these burners might be provided, each "of them being operated and working in the manner previously specified.

, "Combustion chambers,.with the improve ments which are thesubject of the present invention, offer the further advantage that, they canv be constructed with reduced dimensions in comparison with those existing for the same tonnage of coal burnt.

What I claim is 1. In combination with a furnace for pulverized fuel, said furnace comprising an upper combustion zone portion and a lower neutral zone portion, a burner, means for forcing pulverized fuel to said burner, a connecting pipe leading from said forcing means to said burner, means for producing a continuous flow of free air across the lower zone of said furnace, and means for causing said air to enter said connecting pipe.

2. In a furnace comprising an upper combustion-zone portion, a lower neutral-zone portion situated below said upper portion and in open communication therewith, and burners supplying the mixture of air and pulverized fuel into said combustion zone portion of the furnace, the combination of means for producing a flow of free air in the form of a horizontal layer across the lower portion of the furnace, said air forming a heat intercepting screen traversed by cinders falling from the combustion zone, and means for causing said air to enter said combustion zone portion of the furnace through said burners.

3. In a furnace comprising an upper combustion-zone portion and a lower neutral zone portion situated below said upper portion and in open communication therewith, the combination of means for feeding pulverized fuel into said combustion zone portion, and means for producing a flow of free ir transversely of said neutral zone and below said combustion zone, said air-flow producing means including a. plurality of airinlet openings on one side of said neutral zone and a plurality of air-outlet openings on the opposite side of said neutral zone, and means for applying suction to said air-outlet openings.

at. In a furnace comprising an upper combustion zone portion, a lower neutral zone portion situated below said upper portion and in open communication therewith, and means for supplying pulverized fuel to the combustion zone portion of the furnace, a secondary air supply comprising means for producing a flow of air across the lower zone of the furnace, said air forming a screen traversed by cinders falling from the upper combustion zone of the furnace, said screenforming air being heated both by radiation from the furnace and by the passage of falling cinders, and means for causing said heated air to enter the upper combustion zone portion of the furnace together with said pulverized fuel.

5. The process of pulverized fuel combus tion, which comprises the supply of pulverized fuel to a zone of combustion in the upper portion of a furnace the formation of a horizontal screen of continuously moving air across the lower portion of the furnace and below the zone of combustion therein, allowing the cinders to fall from the combustion zone through said screen of air, thereby cooling said cinders by direct contact with said moving air, and causing the air so heated in its passage across said lower portion of the furnace to enter the combustion zone together with the pulverized fuel for burning in said combustion zone.

6. Method of burning pulverized fuel in a furnace comprising an upper combustion zone and a lower neutral zone, which consists in supplying pulverized fuel to said combustion zone producing a flow of air across the lower zone of the furnace, cooling the cinders falling from the combustion zone by direct contact with said air, and causing the air so heated to be delivered with the pulverized fuel into the combustion zone for burning therein.

In a furnace comprising an upper combustion zone portion, a lower neutral zone portion, situated below said combustion zone and in open communication therewith, and means for feeding pulverized fuel to the combustion zone of the furnace, the combination of means for producing a flow of free air in a continuous horizontal layer transversely of said neutral zone and below said combustion zone, said means including a plurality of air-inlet openings on one side of said neutral zone, a plurality of air-outlet openings at the same level but on the opposite side of said neutral zone, means for applying suction to said air-outlet openings, the air in said layer being traversed and heated by cinders falling from said combustion zone and also by radiation from the upper portion of the furnace, and means for feeding the air from said outlet-openings into said fuel feeding means for admixture with the pulverized fuel.

8. A method of intensifying the combustion of fuel poor in volatile substances and recuperating the heat otherwise lost, consisting in supplying the fuel to a combustion zone in the upper portion of a furnace producing a flow of free air in the form of a horizontal layer moving continuously across the lower portion of the furnace below the combustion zone thereof, cooling the cinders falling from the combustion zone by direct contact with said air layer, and utilizing the air so heated in admixture with pulverized fuel for accelerating the ignition of said fuel and facilitating its burning in the combustion zone of the furnace.

In testimony whereof I hereunto afiix my signature.

EMILE HAVEAUX. 

